JP2012111952A - Non-aqueous solvent-free process for making uv curable adhesive and sealant from epoxidized monohydroxylated diene polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a UV curable adhesive, sealant and coating made from a monohydroxylated epoxidized block polymer comprised of at least two different diene monomers.SOLUTION: The block copolymers of isoprene and butadiene wherein a hydroxyl group is attached at one end of the polymer molecule, and which may be hydrogenated or unhydrogenated, can be epoxidized together with insoluble photoinitiator which is preferably selected from the group consisting of triaryl sulfonium salts to effect rapid UV cure. The mixture is then subjected to mixing conditions in a high speed mixer, preferably a high speed disk disperser, at a blade tip speed of from 200 to 2,000 cm/sec at a temperature from 25 to 130°C, preferably from 40 to 100°C.

Description

  The present invention relates to a new process for producing adhesives and sealants made from monohydroxylated diene polymers. More particularly, the invention relates to such a method in which normally insoluble photoinitiators are incorporated into polymers in very fine microemulsions.

  The use of novel epoxidized monohydroxylated polydienes in UV curable adhesive and sealant compositions and compositions and methods for their preparation are described in US Pat. No. 5,776,998. Such polymers are combined with other ingredients such as tackifying resins to make them suitable for adhesive and sealant products. A photoinitiator is included in this combination to promote UV curing (crosslinking) of the composition. Prior art methods for making such materials included mixing the components in a non-aqueous solvent such as tetrahydrofuran (THF) and then casting an adhesive film from the solution. THF was used because the specific commercial photoinitiator selected (mixed salt of triarylsulfonium hexafluoroantimonate in propylene carbonate) is otherwise not soluble in the adhesive formulation. This is because it was soluble in THF. After the adhesive is solvent cast, the THF is evaporated, the photoinitiator is sufficiently dispersed in the remaining adhesive film, and effective UV curing is initiated when exposed to UV light Had been.

For many applications, the use of non-aqueous solvents is undesirable because it is harmful to the environment and because of the cost of removing the non-aqueous solvent and the non-aqueous solvent itself. US Pat. No. 5,776,998 is epoxidized with the same photoinitiator and other photoinitiators so that an effectively cured adhesive or sealant is produced without solvent problems. A non-aqueous solvent-free method for dispersing in monohydroxylated diene polymer formulations has been described. This method is under high shear conditions in a high shear mixer with a shear rate of at least 38,000 S ^-1 or high shear conditions in a sonicator with a power density of at least 4 Watts / milliliter. Originally included mixing the components without using a non-aqueous solvent.

  According to the method of US Pat. No. 5,776,998, it was possible to achieve a fine dispersion having a droplet size that was less than 10 microns in diameter, as described in that patent. In fact, the best dispersion produced by the method of this patent was able to achieve a dispersion having a suitable liquid size with a diameter of about 0.5 microns. As described in the patent, good UV cured adhesive and sealant products can be produced using dispersions produced by the mixing method described in the patent.

  Experience with such dispersions (emulsions) has shown that it is very important to obtain photoinitiator emulsions with very small particle sizes. Such photoinitiator emulsions that are apparent to be about 0.5 microns in diameter are much more beneficial than emulsions that are 1 micron or more in diameter. Very fine emulsions cure almost instantaneously when the active initiator is used at levels as low as 0.04 weight percent to 0.1 weight percent (wt%) based on the total adhesive formulation It is possible. In addition to the obvious advantage of requiring less of what is the most expensive component of the formulation, its very low level allows the final cured formulation to have maximum thermal stability. . The smaller the residual amount of acid produced by UV exposure of the photoinitiator, the less breakage of bonds in the gel network structure occurs.

  The preferred method of introducing a photoinitiator emulsion into a formulation has heretofore been to make a high concentration emulsion of the photoinitiator in one of the components of the formulation first and then add it as the last component of the formulation Met. There are several advantages to making a high concentration of photoinitiator in advance. First, the photoinitiator emulsion can be examined before use. Second, the emulsion can be prepared at another location where the required equipment is installed. Third, a much smaller amount of material can be processed with a sonicator or a very high shear device, thus reducing the size of the device. Fourth, the exact amount of photoinitiator can be easily added to the formulation. In most cases, a high concentration of photoinitiator is a 5 wt% emulsion of triarylsulfonium hexafluoroantimonate salt in KRATON LIQUID® polymer L-1203 (monool polymer), prepared by sonication. It is. The high concentration of photoinitiator may be a 5 wt% emulsion of the same salt in KRATON LIQUID® polymer L-207 (epoxidized monol polymer), prepared by sonication.

  Several improvements in photoinitiator concentrates and their production have become apparent from industrial work. First, there is a strong need to be able to produce emulsions on devices that have less shear and are readily available than sonicators or very high shear rotor / stator devices. Second, if the high concentration of the photoinitiator emulsion is made in advance or elsewhere, one of the important features of the emulsion high concentration is that under storage and transport conditions. Storage stability. For the above reasons, it is very important to make dispersions that have little tendency to agglomerate and increase particle size. Increased stability is highly desirable. Thirdly, it is always sought to produce an emulsion with a minimum droplet size in order to derive maximum cure for minimal use.

US Pat. No. 5,776,998

  The present invention relates to a method for producing UV curable adhesives, sealants, coatings, inks, flexible printing plates, laminate adhesives, fibers, gaskets, and related compositions, films, and thin parts. It is. In this case, an epoxidized monohydroxylated polydiene polymer composed of at least two different diene monomers, at least one of which is a diene monomer that provides unsaturation suitable for epoxidation, is part of the binder to the composition. used. A preferred epoxidized monohydroxylated polymer is a block copolymer of isoprene and butadiene in which one hydroxyl group is attached to one end of the polymer molecule. Such polymers may be hydrogenated or unhydrogenated.

  The method mixes the polymer with an insoluble photoinitiator, preferably selected from the group consisting of triarylsulfonium salts, or mixes the polymer with such a photoinitiator with one or more other ingredients. Including doing. The mixture is then relatively heated in a medium to high speed mixing device at a temperature of 25 ° C. to 130 ° C., preferably at a temperature of 40 ° C. to 100 ° C., with a blade tip speed of about 200 cm / sec to 2000 cm / sec. Subject to low shear mixing conditions. The method is a stable, usually consisting only of photoinitiator and epoxidized monol polymer, usually added to adhesives, coatings, sealants, and other formulations to allow rapid UV curing. It is very suitable for making high concentrations of cationic photoinitiators. The dispersed photoinitiator droplets are less than 1 micron in diameter, preferably 0.5 microns or less, and are preferably uniformly dispersed in the emulsion concentrate.

  A variety of polymers containing ethylenic unsaturation can be prepared by copolymerizing one or more olefins (particularly diolefins) with themselves or one or more alkenyl aromatic hydrocarbon monomers. Of course, such copolymers can be linear, star or radial, as well as random, tapered, block or combinations thereof.

  In general, when solution anion technology is used, the monomer (s) to be polymerized simultaneously or sequentially with a copolymer of a conjugated diolefin with a vinyl aromatic hydrocarbon, if necessary, are group IA. It is prepared by contacting with an anionic polymerization initiator such as a metal (preferably lithium), an alkylated product thereof, an amide, a silanolate, a naphthalide, a biphenylated product or an anthracenyl derivative. Monohydroxylated polydienes are synthesized by anionic polymerization of conjugated diene hydrocarbons using these lithium initiators. This method is well known as described in US Pat. No. 4,039,593 and Reissued Patent No. 27,145, the descriptions of which are incorporated herein by reference. . The polymerization is initiated by a monolithium initiator that assembles the living polymer backbone at each lithium site.

  Conjugated diolefins that can be anionically polymerized include such conjugated diolefins containing from about 4 to about 24 carbon atoms, such as 1,3-butadiene, isoprene, piperylene, methylpentadiene, Phenylbutadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadiene and the like are included. Isoprene and butadiene are preferred conjugated diene monomers used in the present invention because they are low cost and can be easily obtained.

The monohydroxylated polydiene polymer of the present invention has the following structural formula:
(I) (HO) _x -AB- (OH) _y
Where A and B are polymer blocks that can be homopolymer blocks of conjugated diolefin monomers or copolymer blocks of conjugated diolefin monomers. In general, it is preferred that the A block has a higher concentration of more highly substituted aliphatic double bonds than the B block has. Therefore, the A block has a higher concentration of disubstituted, trisubstituted or tetrasubstituted unsaturated sites (aliphatic double bonds) than the B block has per unit block mass. This gives a polymer where maximum surface epoxidation occurs in the A block.

  The A block has a molecular weight of 500 to 4,000 (preferably 1000 to 3000), and the B block has a molecular weight of 2000 to 10,000 (preferably 3000 to 6000). x and y are 0 or 1. Either x or y must be 1, but only one can be 1 at a time. Either the A block or the B block is capped with polymer mini-blocks of different compositions and molecular weights of 50 to 1000 to compensate for any initiating or undesired gradual decay or capping difficulties due to unfavorable copolymerization rates. be able to. Such polymers can be epoxidized to contain 0.5 to 4 milliequivalents (meq) of epoxy per gram of polymer.

Diblocks included in the above description are preferred. The overall molecular weight of such diblocks prior to hydrogenation and epoxidation can range from 2500 to 14,000 (preferably 3000 to 7000). For example, if I represents isoprene, B represents butadiene, and the slash (/) represents a block of a random copolymer, the diblock may have the following structure:
B _{low vinyl-} B _{high vinyl-} OH, I-B-OH, II / B-OH
These diblocks are advantageous in that they exhibit good viscosity for preparing high concentrations of photoinitiators. It is preferred that the hydroxyl be bound to the butadiene block. This is because epoxidation proceeds more favorably with isoprene and the functional groups on the polymer are separated. This gives a more characteristic surfactant-like molecule that can also cure at both ends. KRATON LIQUID® L-207 is a hydrogenated and epoxidized IB-OH polymer that can be obtained in commercial quantities. This is within the preferred range for the I block and B block. Its overall molecular weight before epoxidation and hydrogenation is about 5400 to 6600.

  Epoxidation of the base polymer can be carried out by reaction with an organic peracid that can be produced in advance or an organic peracid that can be produced in situ. Suitable peracids that have been produced in advance include peracetic acid and perbenzoic acid. In situ production can be achieved by using low molecular weight fatty acids such as hydrogen peroxide and formic acid. These and other methods are described in more detail in US Pat. Nos. 5,229,464 and 5,247,026, which are incorporated herein by reference. The amount of epoxidation of these polydiene polymers ranges from 0.5 milliequivalent to 4 milliequivalents of epoxide per gram of polymer. Lower levels are desirable to avoid overcuring. Above 4 meq / g, stiffness, crosslink density, cost, manufacturing difficulty, and polymer polarity (polarity that does not allow certain monohydroxydiene polymers and does not dissolve the photoinitiator) are large. It will not be profitable because it becomes too much. The preferred epoxidation amount is 1 meq / g to 3 meq / g, and the most preferred epoxidation amount is about 1.4 meq / g to 2.0 meq / g for KRATON LIQUID® L-207. The most preferred amount provides the best balance of cure to overcure ratio and better maintains compatibility with various compounding ingredients commonly used with polydiene adhesives. Furthermore, an excellent photoinitiator emulsion is obtained with the most preferred amount. Epoxidation can somewhat increase the molecular weight and viscosity of the diblock due to the formation of dimers and trimers. This is not detrimental to the present invention.

  The molecular weight before coupling of a linear polymer, or an unassembled linear segment of polymer (eg, a star polymer arm, such as a monoblock, diblock, triblock, etc.) can be Conveniently measured by gel permeation chromatography (GPC). In the case of an anionically polymerized linear polymer, the polymer is essentially monodisperse (the ratio of weight average molecular weight / number average molecular weight is close to 1). For low molecular weight functionalized polymers, the number average molecular weight should be calculated from the chromatograph, especially if the polymer is slightly polydisperse due to dimer and trimer formation. is there. For materials used in GPC columns, styrene-divinylbenzene gel or silica gel is generally used and these are excellent materials. Tetrahydrofuran is an excellent non-aqueous solvent for the types of polymers described herein. A refractive index detector can be used. GPC calibration can be performed on several polymers of the same type by first measuring the number average molecular weight by proton NMR.

  If desired, these block copolymers can be partially hydrogenated. Hydrogenation can be done selectively as disclosed in US Reissue Patent 27,145, which is incorporated herein by reference. Hydrogenation of these polymers and copolymers can be achieved with catalysts such as Raney nickel, noble metals such as platinum, soluble transition metal catalysts and titanium catalysts such as in US Pat. No. 5,039,755 (also incorporated by reference). Can be performed by a variety of well-established methods, including hydrogenation in the presence of The polymer can have various diene blocks, and these diene blocks are selected as described in US Pat. No. 5,229,464, which is also incorporated herein by reference. Can be hydrogenated. Partially unsaturated hydroxylated polymers are further functionalized to make the epoxidized polymers of the present invention useful. Partial unsaturation is preferably performed so that 0.5 meq to 4 meq of aliphatic double bonds suitable for epoxidation remain on the polymer. When epoxidation is performed and then hydrogenated, it is preferable to hydrogenate all remaining aliphatic double bonds.

  The binder of the present invention can be cured by cationic means using an acid catalyst, but is preferably cured by ultraviolet irradiation or electron beam irradiation. Radiation curing using a wide variety of electromagnetic wavelengths is possible. Either ionizing radiation (alpha rays, beta rays, gamma rays, x-rays, etc.) and high energy electrons or non-ionizing radiation (ultraviolet rays, visible rays, infrared rays, microwaves and radio frequencies, etc.) can be used. A complete description of how this irradiation can be achieved is found in commonly owned US Pat. No. 5,229,464, which is incorporated herein by reference.

  When using radiation, it is necessary to use a photoinitiator to initiate the crosslinking reaction. In order to practice the present invention, the photoinitiator must be in liquid form and must be insoluble in at least one of the polymers of the present invention. All currently available sulfonium salt initiators are in liquid form (the initiator is dissolved in propylene carbonate) and will be substantially insoluble in the most preferred polymers of the present invention. Such photoinitiators are also very suitable for emulsification. In contrast, all or most of the iodonium salt photoinitiators currently available have at least some solubility in the polymers of the present invention due to their alkyl chains or cations used, and thus the present invention. Not suitable for. They can be added to the adhesive or sealant formulation as an auxiliary additive provided they do not destabilize the emulsion. Photoinitiators useful for emulsification include the following triarylsulfonium hexafluoroantimonate salts: Cyracure UVI-6974 (mixed triaryl type) obtained from Union Carbide, UVE obtained from Von Roll Isola -1014 (mixed triaryl type), ADEKA Optimer SP-170 obtained from Asahi Denka Kogyo Co., Ltd., and Sarcat CD1010 obtained from Sartomer. The following arylsulfonium hexafluoroantimonate salts are also suitable for emulsification, but they are less desirable because of their slower curing: Cyracure UVI 6990 obtained from Union Carbide, UVE-1016 obtained from Von Roll Isola, ADEKA Optimer SP-150 obtained from Asahi Denka Kogyo Co., Ltd., and Sarcat CD1011 obtained from Sartomer. Some soluble iodonium photoinitiators include Sarcat CD-1012 from Sartomer, Rhodorsil R-2074 from Rhodia, hexafluoroantimonate or phosphate salt of (4-octyloxyphenyl) -phenyliodonium, And hexafluoroantimonate salt or phosphate of (4-decyloxyphenyl) -phenyliodonium.

  These onium salts can be used alone or in conjunction with photosensitizers that respond to long wavelength UV and visible light. Examples of photosensitizers include thioxanthone, anthracene, perylene, phenothiadione, 1,2-benzoatracene, coronene, pyrene and tetracene. The dispersion / emulsion of the present invention may contain up to 40% by weight or more of photoinitiator.

  In accordance with the present invention, the insoluble photoinitiators described above can be applied to the polymers described above to produce a composition that can be radiation cured without the need for non-aqueous solvents. Can be dispersed together with other components such as a tackifier. The polymer, optional resin, and photoinitiator are mixed in a mixing device under moderate shear mixing conditions, albeit at high speed.

  Mixing is performed at a blade tip speed of 200 cm / sec to 2000 cm / sec. If the mixing speed is less than about 200, some of the emulsified droplets can be larger than 1 micron in diameter. This slows the initial cure and reduces the self-life of the product. If the mixing speed is roughly greater than about 2000 cm / sec, unnecessary heat is generated. The thermal energy that is not removed raises the temperature of the emulsion, which tends to negate any potential beneficial effect of higher tip speeds. The limit maximum tip speed is not a well-defined value. The critical maximum tip speed can greatly suggest how fast it is expected to produce more heat than can actually be removed in a manufacturing situation. The blade tip speed is determined by the diameter of the disk (blade, impeller) and the rotational speed rpm of the shaft. Commercial high speed dispensers can deliver up to 5000 ft / min (2540 cm / sec).

  The preferred tip speed for the present invention is from 300 cm / sec to 1500 cm / sec, most preferably from 800 cm / sec to 1200 cm / sec. The temperature during mixing can range from 25 ° C. to 130 ° C., but preferably ranges from 40 ° C. to 100 ° C., and most preferably ranges from 50 ° C. to 80 ° C. If the temperature is higher than 130 ° C., too many of the particles tend to have a diameter greater than 1 micron. An emulsion concentrate is considered a microemulsion when it is not made at least near the critical minimum speed and critical maximum temperature of the present invention. Typically, the microemulsion has an upper phase transition temperature at which the microemulsion is no longer stable and thus the droplets become large. For the emulsion concentrates of the present invention, the phase change temperature is probably due to the high viscosity / molecular weight of the polymer used or due to the special functionality of the polymer “surfactant” being used. It is not abrupt but moderate. If the emulsion is damaged by excessive temperature, the “microemulsion” of the present invention can be easily reformed by lowering the temperature and simply mixing.

Examples of mixing devices in which the present invention can be implemented are the most commonly available devices that can achieve blade tip speed and have some heating and cooling capabilities. One preferred example for use in the present invention is the Hockmeyer mixer, which is a high speed disc dispenser that is commonly used at shear rates well below 1000 sec- ¹ to mix paint and pigment dispersions. A variety of high speed dispensers are available from Temple C., published by John Wiley & Sons in 1979. It is described in Paint Flow and Pigment Distribution by Patton. It is clear that they are commonly operated in laminar flow and therefore cannot produce shear turbulence conditions as great as 10,000 seconds- ¹ .

  The apparatus may also have a lid for limiting UV light exposure. Other extensions include a vacuum kettle for defoaming and UV light limitation, another low speed mixing element to premix ingredients to avoid initial overheating, and transfer of viscous material to the high speed blade area. Additional shafts are included, each with its own disk to assist.

  The process of the present invention appears to produce a very stable microemulsion of initiator. Microemulsion droplet sizes are often less than 0.5 microns and most are very small, at least initially, so use an optical microscope in transmission mode at 2000x with white light Cannot be detected. In general, such an optical microscope can only distinguish particles larger than 1 micron. Nevertheless, the presence of particles or structures smaller than 1 micron in diameter is caused by quasiparticles (blurred light and dark) resulting from light scattered or reflected by small droplets of initiator or by agglomerates of small droplets. It can be detected by observing the dot. Nothing can be detected when the size becomes smaller (considered to be about 0.5 microns) or the collection of small droplets stops. Obtaining a droplet size of less than 0.5 microns is necessary to achieve good UV curing of the final composition and the best storage stability for high concentrations of photoinitiator emulsion, along with uniform dispersion of the droplets Very important. The presence of such droplets and their distribution can only be detected by a much more complex device when these small sizes are achieved. A Leica TSC confocal laser scanning microscope can be used in reflection mode to image such emulsion particles.

  It is common practice to add an adhesion promoting or tackifying resin that is compatible with the polymer, generally from 20 to 400 parts per 100 parts of polymer. A common tackifying resin is a diene-olefin copolymer of piperylene and 2-methyl-2-butene having a softening point of about 95 ° C. This resin is commercially available under the name Wingtack® 95 and, as taught in US Pat. No. 3,577,398, 60% piperylene, 10% isoprene, 5% cyclohexane. It is prepared by cationic polymerization of pentadiene, 15% 2-methyl-2-butene and about 10% dimer. Other tackifying resins can be used, in which case such resinous copolymers comprise 20% to 80% piperylene and 80% to 20% 2-methyl-2-butene. . These resins typically have a ring and ball softening point between about 80 ° C. and 115 ° C. as measured by ASTM method E28.

  Hydrogenated resins are usually used when the polymer itself is hydrogenated. Useful hydrogenated resins include Regalrez® resins obtained from Hercules. It is produced by selective hydrogenation of a base resin that has been polymerized using a styrene type comonomer. The degree of hydrogenation ranges from 30% to 100%. The softening point varies from 18 ° C to 140 ° C. Other useful resins include Regalite® resin made by selective hydrogenation of a base polymer polymerized from a mixed aromatic monomer feed stream. The softening point varies from 90 ° C to 125 ° C. Regalite® T and V resins are also useful. Arkon® P series resins obtained from Arakawa are also useful. Other useful resins include polyterpene resins and liquid resins such as Adtac LV and Piccolyte® S25 from Hercules.

  Aromatic resins are also used as tackifiers if they are compatible with the particular polymer used in the formulation and do not appreciably interfere with the UV light transmission or solubility balance of the photoinitiator droplets. Can be used. Typically, such aromatic resins should also have a ring and ball softening point between about 80 ° C. and 115 ° C., although mixtures of aromatic resins having high and low softening points may also be used. it can. Useful resins include coumarone-indene resins, polystyrene resins, vinyltoluene-α-methylstyrene copolymers and polyindene resins.

  The components of the present invention that are used as needed are stabilizers that inhibit or retard pyrolysis, oxidation, skin formation and color formation. Stabilizers are typically added to commercially available compounds to protect the polymer from thermal degradation and oxidation during preparation of the composition, use and storage at elevated temperatures.

  The adhesive is often a thin layer of an adhesive composition (adhering two materials) used in a protected environment. Thus, epoxidized polymers that are not hydrogenated usually have sufficient stability, and therefore the resin type and concentration are selected for maximum tack without significant concern for stability. However, pigments are not normally used.

  Sealant is a gap filler. Thus, the sealant is used in a fairly thick layer to fill the space between the two materials. Since two such materials often move relative to each other, sealants are usually low modulus compositions that can withstand this movement. Since sealants are often exposed to the weather, hydrogenated epoxidized polymers are usually used. Resins and plasticizers are selected to maintain a low modulus and minimize fouling. Fillers and pigments are selected to provide adequate durability and color. Since the sealant is applied in a fairly thick layer, the non-aqueous solvent content is as low as possible to minimize shrinkage.

Examples The materials used in the following examples include:
1. Both KRATON LIQUID® polymers L-1203A and L-1203B are hydrogenated polybutadiene monools in which one hydroxyl group is located at one end of the molecule. A has a number average molecular weight of 3750 and B has a number average molecular weight of 3500.

  2. KRATON LIQUID® polymer L-1302 is a hydrogenated isoprene-butadiene block copolymer having a number average molecular weight of about 6400.

  3. KRATON LIQUID® polymer L-207 is polymer L-207 except that it is epoxidized primarily in the isoprene block so that about 1.7 meq of epoxy is present on the polymer per gram of polymer. Same as 1302.

  4). UVI-6974 is a photoinitiator manufactured by Union Carbide, which is a triarylsulfonium hexafluoroantimonate.

  5). UVE-1014 is a triarylsulfonium hexafluoroantimonate, Von Roll Isola USA, Inc. Is a photoinitiator obtained from This is interchangeable with UVI-6974.

  6). SP-170 is a photoinitiator obtained from Adeka that appears to be similar to UVI-6974.

  7). Regalite® R-91 is a hydrogenated mixed aromatic tack produced by Hercules by selective partial hydrogenation of a base resin polymerized from a mixed aromatic monomer feed stream. It is an imparting resin. It has a ring and ball softening point of 88 ° C.

  In most of the experiments described below, the mixing was done on a Hockmeyer laboratory / pilot scale two horsepower mixer. This 2-horsepower device is capable of mixing approximately 1 to 4 gallons of paint formulation or adhesive formulation, and a single shaft with a 4 inch diameter flat toothed blade attached ( In some experiments, a 4 inch diameter alternative blade consisting of three flat surfaces welded by two sets of fins between the three surfaces was used), a single speed electric motor, and a shaft A belt / pulley system for controlling the speed of the machine. This mixer can achieve a continuous axial speed between 600 rpm and 1900 rpm.

  A laboratory 77 watt electric mixer with a small impeller was also used. The rotational speed of the shaft can be varied between about 650 rpm and 1850 rpm. The impeller blade diameter was 1.5 inches.

  The primary microscope used was equipped with white light, Plan100 / 1.25 oil objective lens, Miroimage Video Systems' Automatic A106A video, Sony Trinitron high-resolution color video monitor and Toshiba HC-1200A color video printer (1980 model) ) The top model of Zeiss microscope. This microscope cannot clearly distinguish photoinitiator droplets that are smaller than about 1 micron in diameter, but can detect the presence of droplets or droplet aggregates that are smaller than 1 micron. Droplets smaller than about 0.5 microns and associated droplets cannot be detected. The very latest Leica TSC confocal laser scanning microscope was also used. This was used in reflection mode to image such emulsion particles. The microscope was equipped with a 63X oil immersion lens. This lens had a depth of focus of 0.4 microns and a lateral resolution of 0.15 microns. This microscope can detect droplets as small as about 0.2 microns in diameter. This microscope was used when available to observe microemulsion details that could not be seen using a Zeiss microscope. A short scan time was used because the motion of the droplets in the liquid medium blurs the droplets.

Example 1 (comparative example)
This experiment shows the limitations of the prior art methods as described in US Pat. No. 5,776,998 for making photoinitiator dispersions. A 50 gram batch of the photoinitiator emulsion was used to separate the UVI-6974 photoinitiator and both L-1203A and L-1203B polymers in separate experiments, using the Prepared with a sonicator (Branson 450 Sonifier). 2.5 grams of photoinitiator and 47.5 grams of polymer were weighed, placed in a small bottle and heated in an oven to 135 ° C., then sonicated for 1 minute and cooled. The results are shown in Table 1 below for the two polymers. As can be appreciated, and as discussed in the '998 patent, an emulsion with a small droplet size was achieved using L-1203A. L-1203A had a molecular weight (and viscosity) greater than that of L-1203B. This emulsion resulted in a fast cure in the adhesive formulation. On the other hand, emulsions formed using L-1203B are readily recognized as droplets using Zeiss, droplets are as large as 2.5 microns, and become larger when heat aging treated. It was. As shown below, this was not very effective with the same formulation for producing UV curing. This behavior is a good indication of what we have observed using these photoinitiator emulsions. Larger droplets are observed using Zeiss, which corresponds to poorer UV curing. This example also demonstrates the importance of having a specific minimum molecular weight / viscosity to help stabilize the photoinitiator emulsion concentrate. It would be expected that very small droplets would be created instantaneously when using L-1203B by sonication, similar to L-1203A. The fact that no such droplets were observed is because the viscosity is so low that the droplet-droplet collision cannot be delayed, so the dispersion is cooled and micrographed This suggests that the droplets cannot survive stably even for the time required for.

Example 2 (comparative example)
As another comparative example, the obvious problem of the viscosity of the continuous phase being too low was the sonication of UVI-6974 to show the resin used in cationic UV curable adhesives using this type of polymer. It was investigated by attempting to add to a tackifying resin that exhibits good characteristics. Regalite® R-91 has a lower molecular weight than polymer L-1203B (M _n = 3500) (M _n is about 600) and is solid at room temperature. 2.0 grams of UVI-6974 and 38.0 grams of Regalite® R-91 tackifier resin were added to a small glass bottle, heated to 135 ° C. and sonicated for 1.5 minutes. A sample was taken out and placed on a microscope slide glass, and a cover glass was placed thereon. The sample solidified immediately. The rest was poured onto release paper and allowed to solidify almost immediately. The mixture had a very low viscosity during the sonication stage and very small droplets may have formed instantaneously, but most of the dispersed photoinitiator was large droplets. See the results shown in Table 2 below. In this case, the size of the emulsion droplets detectable with Zeiss ranged from 0.5 microns to 2.4 microns.

Example 3
A small amount of UVI-6974 photoinitiator (5 percent of the mixture) was dispersed in the L-207 epoxidized polymer using the Hockmeyer mixer described above. The polymer was transferred to a stainless steel pot and heated in an oven at 100 ° C. The pot was placed on the hot plate under the mixer, using the hot plate, and heated to 135 ° C. with slow mixing. When the mixture reached 135 ° C., the shaft speed was increased to 1800 rpm. While maintaining at 1800 rpm, the photoinitiator was added slowly over about 10 minutes. The mixture was mixed for an additional 10 minutes at 1800 rpm while maintaining the batch temperature at about 135 ° C. The mixer was stopped and a small sample was taken and observed with a Zeiss microscope. Photoinitiator droplets were in the desired 0.5 to 1.0 micron range, as reported in Table 3 below. After 2 hours, the batch temperature had dropped to 65 ° C. At that time, another sample was taken and observed with a microscope. No change could be observed. The size, number and distribution of particles appeared to be the same. The droplet size and distribution seemed consistently about the same as those obtained when the dispersion of photoinitiators was made by sonication.

  Microemulsions usually have an upper temperature limit where the microemulsion breaks at higher temperatures. In many cases, the temperature is in the range of 70 ° C to 100 ° C. Assuming that the interaction of the photoinitiator with the L-207 polymer has some special importance in this case, perhaps even suitable for the formation of microemulsions, the mixer was returned and operated . The speed reached 2050 rpm in a short time (about 3 minutes). This was too early for the belt / pulley system to handle and the drive belt came off the pulley and was broken. Unfortunately, the blender only operated for 3 minutes when the belt broke. However, this was advantageous because there was little time for the temperature to rise significantly above 65 ° C. A sample was taken from the pot for microscopic examination but did not have any great expectations due to the short mixing time. Surprisingly, the emulsion was dramatically improved even when the mixing time was only extremely short. Almost all of the photoinitiator droplets could not be seen with a Zeiss microscope. Clearly, a much finer emulsion was produced than the emulsion previously achieved by sonication. Therefore, temperature was considered a very important factor.

  With a Hockmeyer mixer or similar device, the apparently lower shear allows the L-207 polymer to be well mixed at temperatures as low as 65 ° C. without increasing the temperature, yet still much finer So perhaps a more stable emulsion can be made. The Hockmeyer mixer was operated under laminar flow conditions. Under laminar flow conditions, the maximum shear rate R is equal to the tip velocity (expressed in cm / se) divided by the separation distance (expressed in cm) between the disc and the bottom of the mixing tank. The typical distance between the disk and the bottom of the tank that gives a typical flow pattern is 0.5 to 1.0 times the disk diameter, which is from 5.08 cm to 10.16 cm for a 4 inch blade. Correspond. Thus, the maximum shear rate observed in each mix is roughly the tip speed divided by 5.08 cm.

  As a final test to determine the usefulness of this particular emulsion, a small amount is added to the pressure sensitive adhesive (the active photoinitiator is 0.04 weight percent of the formulation), and then the warm adhesive is exposed to UV light. Exposed. The adhesive cured almost instantaneously. The adhesive was completely cured by touch within 20 seconds after a short exposure.

Example 4
In this experiment, an alternative blade was used for the Hockmeyer mixer. This was a 4 inch diameter blade consisting of three flat faces welded together by two sets of fins between the three faces. The manufacturer's literature suggests that this blade arrangement provides a slightly greater shear than other blades.

  Three polymers (L-1302, L-207 and L-1203) were compared for their ability to disperse the insoluble photoinitiator UV-6974. The photoinitiator was dispersed into each of these polymers using an increased rate as shown in Table 4 below. As can be seen from the table, only L-207 was effective in producing very fine droplet size emulsions. The resulting droplets were actually very small and could not be observed using a Zeiss microscope. This emulsion appeared more like a microemulsion than any of the normal emulsions formed by applying very large shear. The other two polymers resulted in coarse emulsions that were not commercially acceptable. They were slow to cure and had a very short lifetime. This is because larger droplets quickly capture the remaining smaller droplets and prevent curing. This triple ring blade was suitable for making very small good emulsions using insoluble photoinitiator and polymer L207, but seems to be as effective as the simpler flat blade used previously. There wasn't. Flat blades appear to be more suitable for producing very fine emulsions that result in slightly less shear and a slightly greater mixing action and are the desired result of the present invention.

Example 5
The triple ring blade was removed and replaced with a previously used tooth-like flat blade. Two of the emulsions of Example 4 (-69 and -70) were weighed and placed in a pot at a ratio of 5 parts of the emulsion containing L-207 and 95 parts of the emulsion containing L-1302. The mixture was heated to 60 ° C. and then mixed at 1800 rpm for 20 minutes. A small amount was removed and examined for droplet size. The presence of just 5 parts of L-207 / photoinitiator dispersion is fundamental to the emulsion (as compared to the L-1302 emulsion of Example 4), as shown in Table 5 below. It was enough to improve. In another experiment, L-207 emulsion was further added to the pot to a new mixing ratio of 20 parts of the emulsion to 80 parts of L-1302 emulsion. Again starting at 60 ° C., the mixture was mixed at 1800 rpm for 20 minutes. The resulting emulsion was so improved that it seemed indistinguishable from the 100 percent L-207 / photoinitiator emulsion of Example 4 as can be seen in Table 5 below. This indicates that the interaction between L-207 and the photoinitiator is particularly satisfactory and only 20 percent of the polymer available in the emulsion concentrate must be L-207. Again, the occurrence of small size emulsions at low mixing temperatures suggests that microemulsions have occurred.

Example 6
In order to further clarify the most desirable mixing temperature to make a special emulsion of L-207 / photoinitiator, batch treatments were made using 60 ° C. and 90 ° C. as mixing temperatures. The results are shown in Table 6 below. Obviously, 90 ° C. is an acceptable temperature, but it can be understood that it is not as good as 60 ° C. The results in the table also consistently show that better emulsions are formed by mixing at a higher axial speed (greater blade tip speed) as long as the temperature can be controlled.

Example 7
When using the previous sonication method, when the photoinitiator addition was greater than 5 weight percent, the emulsion was very unstable and not suitable for commercial use. In this example, an emulsion of photoinitiator and polymer L-207 was prepared with the addition of 5 weight percent, 20 weight percent and 40 weight percent photoinitiator. The experimental results are listed in Table 7 below. In the table it is understood that excellent emulsions can be prepared with all three additions and that the emulsion is very stable at room temperature. These results show that when the emulsion is stored at 70 ° C. for 1 week, the stability of the emulsion at high temperatures is increased with less addition (ie, 5 percent> 20 percent> 40 percent). As such, it seems beneficial to use a 5 percent addition. However, the temperature until the end of mixing increased as a function of the amount of photoinitiator added. With 40 percent addition, the temperature reached 88 ° C. by the end of mixing. This has already been shown to be less desirable than 60 ° C. in previous examples. It is believed that if the pot is assembled with a cold water jacket or cooling coil, a temperature of 60 ° C. or possibly lower can be maintained and the 70 ° C. stability test sample may appear to be significantly improved. It is done. High concentrations affected by heat aging should be able to be fully restored to their original state by simply remixing them as directed by the present invention.

Example 8
This example includes a comparison of the sonication method of the '998 patent with the method that is the subject of the present invention. A 4000 gram batch of the emulsion of the present invention was prepared on a Hockmeyer mixer equipped with a flat toothed 4 inch diameter blade. 3800 grams of L-207 polymer was added to a stainless steel pot and heated to 65 ° C. 200 grams of photoinitiator UVE-1014 was added slowly with the mixer set at about 600 rpm. After the addition was complete, the mixer speed was increased to about 1950 rpm and the batch was mixed for 20 minutes. Air cooling was used, but the final batch treatment temperature reached 79 ° C. The mixer was stopped and the batch processed product was packed into a tan container for storage.

  A 50 gram batch of the photoinitiator emulsion was prepared on the sonicator described above using UVE-1014 and L-207 polymers in the following manner. 2.5 grams of photoinitiator and 47.5 grams of polymer were weighed, placed in a small bottle, heated to 135 ° C. in an oven, and then sonicated for 1 minute. The mixture was cooled for 2 minutes and then sonicated again for an additional 1 minute. The maximum temperature reached was 187 ° C. Double sonication was used because the viscosity of L-207 polymer is high enough so that it is visually apparent that a single sonication for 1 minute does not produce a uniform mixture. Also, a 50 gram batch of the emulsion was treated with the same photoinitiator and polymer, except that only one minute sonication cycle was required due to the lower viscosity of the L-1203 polymer. L-1203 was made using the same method. The highest temperature reached was 171 ° C. These three batches were examined using an optical microscope. The results are shown in Table 8 below. It can be seen that the method of the present invention results in droplets that are much smaller than droplets produced by prior art sonication methods.

Example 9
A 5% emulsion photoinitiator concentrate was made using EKP-206 epoxidized monol polymer and UVE-1014 as the initiator. EKP-206 is not an example of the present invention because it contains polymerized styrene in the second block. This has about 1.5 meq / g of epoxy. EKP-206 is much more viscous than L-207 at room temperature because it has a higher glass transition temperature, but is similar to that of L-207 because it has approximately the same molecular weight above about 100 ° C. is doing. It was expected that it would be more difficult to keep the temperature in the most preferred range of the present invention, which is 50 ° C to 80 ° C. As in some of the previous examples, a Hockmeyer high speed dispenser was used. 3800 grams of EKP-206 was placed in a stainless steel container and warmed to about 60 ° C. in an oven. The container was placed under a Hockmeyer device with a 4 inch flat blade placed in the liquid and stirred at 625 rpm. When the material was well stirred, 200 grams of UVE-1014 was added over 5 minutes at a temperature of 69 ° C. The mixture was mixed for 20 minutes. Mixing was stopped briefly, samples were taken for microscopy and the speed was increased to about 1200 rpm. Mix the mixture for another 20 minutes. The mixer was stopped for a short time and a sample was taken. Thereafter, the mixing speed was increased to about 1800 rpm and mixing was continued for another 20 minutes, after which mixing was stopped. The final temperature of the emulsion was 84 ° C. In the table below, the details of the conditions are shown and the results of Zeiss microscopy are shown. An emulsion having a droplet size required by the present invention could not be prepared. Since the droplets were so large that few were photographed, the micrographs taken showed enough evidence to even assume that the particle size decreased with increasing tip speed. Absent.

Example 10
Different low shear mixing devices were used in this example. This device is a laboratory 77 watt electric stirring motor with a lab type 3 vane (round) impeller blade, with 3 vanes flat but rotating at a fixed angle relative to the liquid Met. The diameter of the circular pattern provided by the rotating blade was 1.5 inches. Weigh 95 grams of L-207, place in a Pyrex® beaker, warm, place on hot plate under mixer and mix at 650 rpm until a temperature of 66 ° C. is achieved Mix at the lowest speed of the machine. 5.0 grams of UVE-1014 was added and mixing was continued for 20 minutes. The mixer was stopped for a short time and a sample for microscopy was taken. The mixer was raised to the maximum speed (1650 rpm) that could be generated under load conditions and the emulsion was mixed for an additional 30 minutes. The beaker was removed from the mixer and the bottom and sides were examined to ensure that all of the photoinitiator was mixed. An excellent emulsion high-concentration product of the present invention was obtained when the mixing speed was increased. Emulsions formed at lower speeds were considered non-standard quality, just outside the scope of the present invention, as judged by droplet size on a Zeiss microscope. See the table below.

  Contrasting examples were prepared in the same way as possible using L-1203 polymer. 95 grams of L-1203 was added to the Pyrex beaker, placed under the same mixer, and heated until the polymer temperature reached 65 ° C. and mixed. 5.0 grams of UVE-1014 was added and mixed for 20 minutes at the minimum speed at which the mixer operated (in this case 650 rpm). The mixer was stopped briefly and a sample was taken for microscopy. The sample was very transparent to the naked eye. This indicates that the photoinitiator has settled to the bottom of the beaker or that the emulsion formed is very coarse. The mixer was started again and the mixture was mixed for 20 minutes at the maximum speed obtained from the mixer (in this case 1850 rpm). The final mixing temperature was 67 ° C. Small size emulsions as achieved by the present invention were not formed. See the table below.

Claims (12)

  A method for producing a UV curable adhesive composition, coating composition or sealant composition, said composition comprising a monohydroxylated epoxidized polydiene block copolymer comprising at least two different diene monomers and If necessary, other compounding ingredients are included, the at least two different diene monomers being at least one diene monomer that provides suitable unsaturation for epoxidation, and the polymer is from 0.5 milliequivalent per gram polymer. Mixing conditions containing 4.0 milliequivalents of epoxy, said epoxidized polymer and, if necessary, a photoinitiator insoluble in the polymer and a blade tip speed of 2000 to 2000 centimeters / second Mixing at a temperature between 25 ° C and 130 ° C Including the method.   The method of claim 1, wherein the blade tip speed is from 300 cm / sec to 1500 cm / sec.   The method of claim 1, wherein the blade tip speed is from 800 cm / sec to 1200 cm / sec.   The method of claim 1, wherein the temperature is from 40 ° C. to 100 ° C.   The method of claim 1, wherein the temperature is from 50 ° C. to 80 ° C.   The method of claim 1, wherein the polymer is a diblock polymer of isoprene and butadiene, the isoprene block containing most of the epoxidation, and hydroxyl groups are present at the ends of the butadiene block.   The method of claim 6, wherein the polymer has a number average molecular weight of 2500 to 14,000.   The method of claim 7, wherein the polymer has a number average molecular weight of 3000 to 7000.   8. The method of claim 7, wherein the polymer has from 1 milliequivalent to 3 milliequivalents of epoxy per gram of polymer.   The method of claim 9, wherein the polymer has a number average molecular weight of 5400 to 6600 and 1.4 to 2.0 milliequivalents of epoxy per gram of polymer.   The method of claim 1, wherein the insoluble photoinitiator is a triarylsulfonium salt.   The method of claim 1, wherein the mixing device comprises a high speed disc dispenser.